These studies are based on the recent finding that a short amino acid sequence (Arg-Gly-Asp-Ser), which appears to be primarily responsible for the cell attachment activity of fibronectin, is found in other proteins. The adhesive nature of these other proteins is to be studied and the specific involvement of this tetrapeptide sequence in the cell attachment-promoting properties of these proteins determined. Beyond this, work will focus on the structural analysis of adhesive proteins other than fibronectin with respect to their interaction with cells. Specifically, the primary structure of the cell attachment site of vitronectin (serum spreading factor), which has already been purified and characterized in our laboratories, will be determined and that structure compared with the cell attachment site of other cell adhesive molecules. (LB)